Magnetizing-coil



(No Model.)

J. D. IHLDER.

MAGNETIZING COIL. No. 516,204. Patented Mar. 13, 1894.

c OOOOO OOGOOO KQ Q19 L 3 .5. CO O O O J L o 0 Q o OOOOOOOOOQ OOOOOOOOUUNITED STATES PATENT OFFICE.

JOHN D. IHLDER, OF YONKERS, NEW YORK.

MAGNETlZlNG-COIL.

SPECIFICATION forming part of Letters Patent No. 516,204, dated March13, 1894.

Application filed November 18, 1892. Serial No. 452,440. (No model.)

To all whom it vie-cry concern:

Be it known that I, JOHN D. IHLDER, a citizen of the United States,residing at Yonkers, 1n the county of Westchester and State of New York,have invented certain new and useful Improvements in Magnetizing-Goils,of which the following is a specification.

My invention relates to magnetizing coils, and has for its object toovercome and prevent the evil eifects which are due to an inductivecurrent which is set up in the magnetizing coils when the circuit isbroken or the lines of force are caused to rapidly collapse.

It consists in the various features of construction, arrangement andhaving the mode of operation, substantiallyas hereinafter moreparticularly pointed out.

Referring to the accompanying drawings I have illustrateddiagrammatically one application of my invention sufficient to enablethose skilled in the art to understand its general principles, and inthe drawings-- Figure 1, is a diagram showing the circuits of a seriesmotor or similar machine. Fig. 2, is a similar view showing a manner ofconnecting the coils. Fig. 3, is a diagrammatic View of a shunt of acompound motor. Fig. 4, is a conventional indication of circuits andcoils applied to an electric machine.

In operating electric machines provided with magnetizing coils, it iswell known that breaking the circuit of the conductor produces acollapse of the magnetic whirls or lines of force which were produced bythe current, and this collapse of the magnetic whirls creates an electromotive force in the conductor which tends to send a current in the samedirection as the primary current, and this is often designated the extracurrent or spark current. In a magnetizing coil of many turns especiallyone containing an iron core, the electro motive force of this extracurrent often becomes very high, and results in heavy flashing at thebreaking point, and producing disruptive discharges which injure andsometimes destroy the insulation of the coil itself or other circuits ormachines connected with the coil. While this is apparent in amagnetizing coil of whatever nature, it is particularly apparent andobjectionable in the magnetizing coils of electric motors, and when suchmotors are connected in circuitwith other translating devices,especially containing inductive resistance, the results are often quiteserious. These results are particularly apparent in electric motorswhich are used to run elevators and the like, where the circuit of themotor has to be made and broken quite often in the ordinary operation ofthe elevator, and the result has been that not only is the motor of theelevator affected, but other motors in the same circuit or othertranslating devices suffor to a greater or less extent from thesedischarges. It is with the object of preventing these evil results thatmy present invention is made. The intensity of the electro motive forceset up depends upon the suddenness of the collapse of the lines of forceor magnetic whirls, if the lines of force collapse suddenly, thesecondary or extra current often attains a much higher electro motiveforce than the electro motive force of the primary current, but when thecollapse of the lines of forcein the magnetizing coil is producedcomparatively slowly, the evil effects are avoided, the electro motiveforce set up in the conductor being proportioned to the rate of decreaseof the lines of force. Heretofore attempts have been made to overcomethese objections by providing the magnetizing coil with a continuousband of sheet copper or other suitable conductorsurrounding the core,and this copper shell acts in this case as a secondary coil of a singleturn of large cross section short circuited on itself. On breaking theprimary coils, the number of lines of force inclosed in both circuits isdecreased, and an electro motive force is set up in both coils, and thiselectro motive force produces a current in the single turn shortcircuited coil, which current again produces lines of force the same asthe primary current before breaking, and the sudden collapse of thelines of force of the magnetizing coil is overcome to a greater or lessextent. I find however, that better results can be obtained by the useof a short circuited coil of many turns containing practicallythe samecross section of conductor, than by using a solid conductor. This seemsto be based upon the fact that only the outside of the conductor isuseful, and it, therefore, be-

comes advantageous to select a conductor of small size to present alarge surface, and I sometimes employ a secondary coil of fine wireshort circuited on itself wound with or connected to the magnetizingcoil. There are, however some objections to this construction which neednot be recited.

In order to overcome the objections spoken of, and especially inconnection with an electric motor when used for elevators and the like,I wind the magnetizing coil in two directions, that is I apply coils soarranged as to act in opposition to each other and connectedtinshuntrelation to the main magnetizing coil, and this opposing coil is ofhigh resistance or of comparatively few ampere turns relatively to themain coil, so that the ampere turns of the main coil are a great manytimes more than the ampere turns of the opposing coil. Such a windingconstitutes a closed circuit with all the coil magnetizing in the samedirection when the secondary current flows through the coils therebyproducingadecrease of the lines of force on breaking the primarymagnetizing current, as all the turns of thiswinding will be active inmaking the rate of decrease of lines of force low. Of course it will beunderstood that this opposing coil reduces to a slight extenttheefiectiveness of the main magnetizing coil, but I find that theproportions may be readily so chosen and arranged that the linesproduced by the action of the opposing coils is very small and can bepractically ignored. Thus referring to Fig. 1, A represents the maincurrent from any suitable source as a distributing circuit, and B, thearmature of a motor for instance, while 0, represents the mainmagnetizing coil of the field magnets of the motor. D is the breakcircuit, and A the continuation of the distributing circuit. E,represents the opposing coils, and it will be seen that the mainmagnetizing coil and the opposing coil are arranged in shunt relationsto-each other, and normally when the motor is operating, the currentwill flow through these coils in accordance with the well known laws,the resistance and number of turns of the coils E, being so proportionedas to produce little influence on the magnetizing effect of the maincoil. When, however, the circuit is suddenly broken, as at D, the extraor secondary current finds a complete short circuit for itself, andbeing in the same direction in both the magnetizing coil and secondarycoil, it prevents the sudden collapse of the lines of force, and theconsequent destructive or disruptive spark or discharge.

In order to prevent a high diiference of potential between parts of thecoils that might be placed in juxtaposition to each other, and also toinsure the operativeness of the device in case of a breakdown, I furtherconnect the conductor of the main magnetizing coil with the conductor ofthe opposing coils.

In Fig. 2, I have shown diagrammatically, portions of the conductor ofthe magnetizing coil'O, and connected to portions of the conductor ofthe opposing coils E, by means of the connectors F, and it will thus beseen that in this way this prevents a high diiterence of potentialbetween the portions of the two conductors, and if, for instance, aportion of either of the coils should be broken at one place, thatsection only would become inactive, and the other sections would operatetogether in the usual manner.

, WhileI have thus shown my improvement as applied to a series woundmotor, it is evldent that the same efiects and results would be obtainedif the opposing coil was used in connection. with an ordinary shuntwound motor and this application of my invention needs no furtherdescription or illustration. At present, however, it is the usualpractlce to use in connection with electric elevators a compound woundmotor, and in Fig. 3,1 have illustrated diagrammatically such a winding,

where the parts are indicated as before, with the addition of the shuntcoil G, connected to the main circuits outside the armature and theseries magnetizing coils, and I find th s a very eifective arrangement,as I find it 1s 1mmaterial whether the coil itself has been active inproducing the lines of force that must be prevented from decreasingrapidly, or whether another coil has produced these lines .of force inpart or in all.

In Fig. 4, I have shown a circuit includm a conventional form of motorhaving the various coils indicated on the field magnets H, connected incircuit with the generator I, and the arrangement thus indicated will bereadily understood by those skilledin the art, and while this may be aconventional way of arranging the coils, of course I do not lim1t myinvention to any particular arrangement or construction, as variousmodifications will readily suggest themselves, and the principles of myinvention can be applied in many and various ways which need not berecited.

While I have shown in the diagram the opposing coil as arranged andextending throughout the magnetizing coils, it is evident that the sameefiects may be produced to a greater or less extent by providing a partonly of the magnetizing coil with the opposing turns. Thus for instancereferring to Fig. 3, the turns represented by E, E might be omitted, andthe action be substantially the same, and other variations of thearrangement of the coils can be employed to suit the exigencies of anyparticular case.

What I claim is- 1. As a means of producing a low rate of change ofmagnetic lines of force, a double magnetizing circuit in shunt relationsto each other, and wound in opposite directions with terminals inpermanent connection, substantially as described.

2. As a means of producing a low rate of change of magnetic lines offorce, a double magnetizing circuit in shunt relations to each other andwound in opposite directions, the

in-umw u terminals in permanent connection and in such proportions thatone circuit has more ampere turns than the other, substantially asdescribed.

3. As a means of producing a low rate of change of magnetic lines offorce, a double magnetizing circuit in shunt relations to each other,and wound in opposite directions, and intermediate connections betweenthese two circuits, substantially as described.

4. As a means of producing a low rate of change of magnetic lines offorce, a double magnetizing circuit in shunt relations to each other andwound in opposition, and intermediate connections between a part only ofthe main magnetizing circuit and the opposing circuit, substantially asdescribed.

5. In an electric machine the combination with the main magnetizing coilor coils, of an opposing coil with terminals permanently connected inshunt with the main coil or coils, and arranged to act with the mainmagnetizing coil when the circuit of the said coil is broken,substantially as described.

6. In a compound wound machine the combination with the main magnetizingcoil, of an opposing coil with terminals permanently connected in shuntthereto and arranged to act with the main magnetizing coil when thecircuit of said coil is broken, substantially as described.

7. In a compound wound machine the combination with the main magnetizingcoil, of an opposing coil of high resistance arranged in shunttherewith, the conductors of the two 3 5 coils being connected togetherat intervals, substantially as described.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

JOHN D. IHLDER.

Witnesses:

JAMEs S. FITCH, JAMES E. IRVINE.

